The modern Porsche change interval is 20k miles. Not sure I agree with the cynicism around longer oil change intervals. The easy thing for manufactures to do is to stick with the old fashioned rules of an annual oil change, though this has no engineering substance at all behind it. Modern engines, fuels and oils have improved significantly over the last 20 years or so and it would be madness to stick with old rules on oil changes.
Though all engineering based rules on these things assumes a certain level of use, so if you are ‘out of family’, so either a very low usage driver or very high usage driver, you may want to deviate from the standard rules. If I were you I’d talk to a respected Porsche specialist and take some advice from them.